Advanced digital reactivity meter for nuclear power plant with WWER reactors

The PC-based DR-8 digital reactivity-meter has been developed jointly by INRNE (Sofia) and IPPE (Obninsk). The input is a neutron flux signal from KNK-56, KNK-53M and KNK-4 ionization chambers in the current range 10-11 A - 10-3 A from analog input channels, and in the range 10+2 - 5x10+5 imp/s from impulse input channels. There is an automatically switch function from impulse channels to an analogue one. The reactivity measurement range is: from -25 βeff to 0.8 βeff. The display of the flux and reactivity values includes digital and analogue indicators on the front panel. Digital signals for power and reactivity can be transmitted to the high-speed PC AT/XT by an optional RS-232 interface. It can work in two regimes: on-line (the data are recorded digitally and are displayed graphically) and off-line (the recorded data are summarized and evaluated by a simultaneous processing to decrease the measurement error from the γ-ray background). The DR-8 reactivity-meter can be used as an accurate device for on-line reactivity control during the reactor physics tests at the initial start-up, refuelling and operation of WWER-440 and WWER-1000. Seven items have been successfully implemented at the Kozloduy NPP. (author)